1. Field of the Invention
The present invention relates to an ink-jet ink which exhibits excellent ejection stability during printing and makes it possible to produce printed matter in which formed text and images exhibit improved abrasion resistance and smoothness, and a recording method using the same.
2. Description of the Related Art
In recent years, since an ink-jet recording system makes it possible to easily form images at lower cost, it has been widely applied to various printing and imaging fields such as photographic imaging, various types of the printing, or special printing such as marking or color filters. Specifically, due to the development of ink-jet recording apparatuses capable of performing controlled ejection of minute ink droplets, ink whose color reproduction range, durability, and ejection adaptability have been improved, minute ink droplets, and special ink-jet paper has markedly enhanced the color formation of colorants, and surface glossiness, whereby the image quality is approaching that of silver salt photography.
However, the image recording system which necessitates special ink-jet paper carries problems in which usable recording media are limited, and the cost of the recording media is relatively high. On the other hand, in an office environment, there has been greater demand for a new system capable of performing full color printing on various recording media at high speed without limitation of recording media (for example, plain paper, coated paper, art paper, and dual side printing on plain paper).
To meet the above demands, required is development of an ink-jet ink which is applicable for various recording media, is capable of high speed printing, results in excellent text reproduction and image quality, and further in excellent retention property of formed images, especially excellent image abrasion resistance.
In order to overcome the above drawbacks, proposed have been various methods. One of the methods is the use of a solvent based ink. By employing an oil ink (being a solvent based ink), the drying properties of which is enhanced via incorporation of volatile solvents, it is possible to produce printed matter which exhibits excellent fixing due to its rapid penetration into recording media and short drying time. However, solvents such as ethyl acetate or methyl ethyl ketone result in unpleasant odor and a large amount of volatile solvents are harmful to operators. Under the present situation in which better office environments are required, it is difficult to use the ink as above.
Listed as another method is the use of a hot-melt type ink. The hot-melt type ink incorporates, as a main component, waxes which are in a solid state at room temperature and when heated, melt to decrease viscosity. Ink which is heated and melted in an ink-jet recording head is ejected and after deposition onto a recording paper, it is cooled and thereby solidified to form printed images. The hot-melt type ink exhibits the advantage in which volatile solvents are not employed. However, due to the use of waxes as a main component, when the surface of the formed image is rubbed, abrasion tends to result. Thus, the hot-melt type ink exhibits problems of insufficient abrasion resistance, whereby it is difficult to apply it to permanent printed matter. Further, additional problems occur in which due to high content ratio of solids such as wax as an ink component, formed text and images build up on the recording medium.
Further, known as another method is one which employs an ultraviolet radiation curable ink-jet ink. The ultraviolet radiation curable ink-jet ink is composed of ultraviolet radiation curable monomers and curing initiators as main components. After printing on a recording media, deposited ink droplets are cured upon being exposed to ultraviolet radiation. Due to the above curing, advantages are exhibited in which abrasion resistance against scratching is enhanced, and further, no volatile solvents are needed. However, many of employed ultraviolet radiation curable monomers result in skin irritation and exhibit sensitizing properties, whereby ink itself results in drawbacks for safety. Further, since the content ratio of solids in the ink is relatively high, problems have occurred in which formed text and images build up on the recording medium.
In addition, disclosed as other methods are a number of methods, to employ latex inks incorporating fine polymer particles (refer, for example, to Patent Documents 1-4). It is known that the above latex inks, which are prepared by incorporating fine polymer particles into an ink in which water is a main component, exhibit excellent adaptability to the environment and excellent abrasion resistance, and further make it possible to produce printed matter in which formed text and images do not build up on the recording media. However, when such latex inks are continuously or intermittently used at relatively low humid conditions, poor ejection from recording heads results due to an increase in viscosity caused by drying ink, whereby problems have occurred in which it is not possible to achieve stable ejection. Further, since the content of fine polymer particles is inherently limited, it is not possible at present to achieve sufficient image durability required for printer matter.
(Patent Document 1) Japanese Patent Publication for Public Inspection (hereinafter referred to as JP-A) No. 9-87560
(Patent Document 2) JP-A No. 9-1767533
(Patent Document 3) JP-A No. 10-60353
(Patent Document 4) JP-A No. 2000-85238
In view of the above problems, the present invention was achieved. An object of the present invention is to provide an ink-jet ink which exhibits excellent ejection stability during printing and enhances abrasion resistance of text and images formed on various recording media and image smoothness, as well as a recording method using the same.